Declared stac

--- a/src/FOL/IFOL.ML	Thu Sep 26 16:38:02 1996 +0200
+++ b/src/FOL/IFOL.ML	Thu Sep 26 17:02:51 1996 +0200
@@ -225,8 +225,9 @@
 (** ~ b=a ==> ~ a=b **)
 val [not_sym] = compose(sym,2,contrapos);
 
-(*calling "standard" reduces maxidx to 0*)
-bind_thm ("ssubst", (sym RS subst));
+(*Substitution: rule and tactic*)
+bind_thm ("ssubst", sym RS subst);
+fun stac th = CHANGED o rtac (th RS ssubst);
 
 (*A special case of ex1E that would otherwise need quantifier expansion*)
 qed_goal "ex1_equalsE" IFOL.thy